Audio data associated with a surface and a position on the surface

ABSTRACT

A method of playing audio data by a portable device is disclosed. The method starts with an optical sensor of the portable device sensing a tag on a surface. The tag encodes an identity of the surface and a location of the tag on the surface. Audio data is recorded by an audio system of the portable device. A processor of the portable device determines the identity of the surface and the location of the tag sensed by the optical sensing device on the surface. The portable device communicates the audio data, the identity of the surface and the location of the tag to a computer system where the audio data is associated with the identity of the surface and the location of the tag. Upon subsequent sensing of the tag by the optical sensor, the portable device communicates the identity of the surface and the location of the tag to the computer system, where the audio data associated with the identity of the surface and the location of the tag is retrieved and communicated to the portable device. The audio data retrieved by the portable device is then played back by the portable device.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Continuation of U.S. application Ser. No. 11/866,305, filed Oct. 2, 2007, which is a Continuation of U.S. application Ser. No. 10/917,466, filed Aug. 13, 2004, now issued U.S. Pat. No. 7,474,930, which is a Continuation of U.S. application Ser. No. 09/722,087 filed on Nov. 25, 2000, now issued as U.S. Pat. No. 6,788,982, the entire contents of which are herein incorporated by reference.

FIELD OF INVENTION

The present invention relates to devices for receiving machine-readable input and for outputting a human discernable output, usually in the form of audio or visual information. More particularly the invention relates to an audio player which may be used to scan or sense machine-readable coded data on a surface and to output audio material in response to the sensed coded data.

CROSS REFERENCE TO OTHER RELATED APPLICATIONS

Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications/granted patents filed by the applicant or assignee of the present invention:

6,530,339 6,631,897 7,295,839 09/722,174 7,175,079 7,064,851 6,826,547 6,927,871 6,980,306 6,965,439 6,788,982 7,263,270 6,788,293 6,946,672 7,091,960 6,792,165 7,105,753 7,182,247 6,712,452 7,110,126 6,813,558 6,965,454 6,847,883 7,131,058 7,190,474 6,982,798 6,474,888 6,627,870 6,724,374 7,369,265 7,533,031 6,808,330 6,527,365 6,474,773 6,550,997 6,824,044 6,454,482 6,963,845 6,995,859 6,720,985 6,622,923 6,394,573 6,679,420 6,678,499 6,976,220 6,976,035 6,766,942 6,398,332 6,922,779 6,978,019 7,406,445 6,959,298 6,973,450 7,150,404 6,965,882 7,233,924 7,007,851 6,957,921 6,457,883 6,831,682 6,428,133 6,526,658 6,315,399 6,338,548 6,540,319 6,328,431 6,977,751 6,859,289 6,318,920 6,488,422 6,795,215 7,154,638 6,328,425 6,991,320 6,383,833 6,464,332 6,390,591 7,018,016 6,328,417 09/575,197 7,079,712 6,825,945 7,330,974 6,813,039 6,987,506 7,038,797 6,980,318 6,816,274 7,102,772 7,350,236 6,681,045 6,728,000 7,173,722 7,088,459 09/575,181 7,068,382 6,957,768 7,456,820 7,170,499 7,106,888 7,123,239 6,409,323 7,062,651 6,789,194 6,789,191 6,644,642 6,502,614 6,622,999 6,669,385 6,549,935 6,987,573 6,727,996 6,591,884 6,439,706 6,760,119 7,295,332 6,290,349 6,428,155 6,785,016 6,870,966 6,822,639 6,737,591 7,055,739 7,233,320 6,830,196 6,832,717 6,281,912 6,604,810

The disclosures of these co-pending applications and patents are incorporated herein by cross-reference.

BACKGROUND

Purpose-specific devices such as radios and audio cassette players, as well as more general-purpose devices such as personal computers and organizers, can be used to play back audio material such as music. Many of these devices can also be used to record audio material, such as voice dictation.

In general, these devices don't provide access to situated audio, e.g. to a music clip associated with a concert poster encountered at a train station, or spoken instructions associated with a page in a workshop manual. Each device must be used to seek out the desired audio material through a virtual space accessible through the device, or the audio material must be brought to the device in a device-compatible physical format.

The present invention utilizes methods, systems and devices related to a system referred to as “netpage”, which is described in our co-pending applications listed above.

SUMMARY OF INVENTION

According to an aspect of the present invention there is provided a method of playing audio data by a portable device, said method comprising the steps of:

sensing, by an optical sensor of the portable device, at least one tag on a surface, the tag encoding an identity of said surface and a location of that tag on the surface;

recording audio data by an audio system of the portable device;

determining, by a processor of the portable device, the identity of said surface and the location of the tag sensed by the optical sensing device on the surface;

communicating by the portable device the audio data, the identity of said surface and the location of the tag to a computer system;

associating, by the computer system, the audio data with the identity of said surface and the location of the tag;

wherein, upon subsequent sensing of the tag by the optical sensor, the method comprises the further steps of:

communicating by the portable device the identity of said surface and the location of the tag to the computer system;

retrieving, by the computer system, the audio data associated with the identity of said surface and the location of the tag;

communicating the audio data from the computer system to the portable device; and

playing back the audio data retrieved by the portable device.

Other aspects are also disclosed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a front perspective view from below of an audio player according to a first embodiment of the invention;

FIG. 2 shows a rear perspective view from below of the audio player of FIG. 1;

FIG. 3 shows a front exploded perspective view from above of the audio player;

FIG. 4 shows a plan view from above of the audio player;

FIG. 5 shows an end view of the audio player;

FIG. 6 shows a side view from the right of the audio player;

FIG. 7 shows a cross sectional side view of the audio player taken along line AA shown in FIG. 4.

FIG. 8 shows a perspective view from below of the PCB of the audio player;

FIG. 9 shows an exploded perspective view from below of the PCB of the audio player;

FIG. 10 shows a perspective view from above of the PCB of the audio player;

FIG. 11 shows an exploded rear perspective view from above of the audio player;

FIG. 12 shows a plan view of a page for use with the first embodiment; and

FIG. 13 shows a block diagram of the electronic components of the audio player.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

Referring to FIGS. 1 to 11 and 13 there is shown an audio player 10. The audio player has a body formed of upper and lower casings 12 and 13 in which is located a PCB 14. Mounted on the PCB are an optical sensor device 16, an alphanumeric display 18, control switches 20, a volume control 15, a speaker 22 and a headphone jack 24. The upper and lower casings 12 and 13 are held together by screws 17 which pass through openings 19 in the upper casing 12, through an aperture 21 in the PCB 14 and into bosses 23 in the lower casing, so securing the two casings and the PCB together. The upper casing has an aperture 25 into which the display 18 and an elastomeric keypad 27 extend. A transparent window 29 overlays the display 18 and both the window 29 and the keypad 27 are held in position by a top cover 131. The cover 131 has an aperture 26 into which the window 29 extends, so the top surface of the window is flush with the top of the cover 131. The cover 131 also extends over the screws 17. The cover 131 is preferably affixed to the top casing by adhesive but may be a snap fit to the top casing. The keypad buttons 28 extend through corresponding apertures 33 in the cover.

The optical sensor device 16 includes an image sensor 30, infrared LED 31, a light guide 32 and lens 34. The near-infrared LED 31 may be strobed in synchrony with image capture to prevent motion-blurring of captured (tag) images. The image sensor 30 typically consists of a 200×200 pixel CCD or CMOS image sensor with a near-infrared bandpass filter. The light guide 32 and lens 34 may be integrally formed or may be separate components. The lens extends out of the body. The free end portion 35 of the light guide 32 is cylindrical and a force sensor collar 37 is slideably mounted on the cylindrical portion. The collar extends beyond the free end of portion 35 so that when the audio player is pushed against the surface the collar rather than the lens 34 contacts the surface.

The collar 37 extends around and behind the optical device 16 and engages a micro switch 39. The micro switch is biased to an open position; pushing on the collar against the micro switch 39 overcomes the biasing means in the switch 39 and closes it. When the force is removed the biasing means urges the collar outward and opens the switch again. A separate biasing means may be provided external of the switch 39 in addition to the micro switch's own biasing means.

The speaker 22 is located in a circular extension 141 at the top of the body and the top casing 12 is provided with a series of apertures 143 to allow sound to be transmitted by the speaker 22.

The extension 141 also serves as a battery compartment 145 and this is accessed by a cover 147 which clips onto the lower casing 13. Power is supplied to the PCB by a rechargeable or disposable battery 44. The battery 44 is located in the compartment 45 and engages battery contacts 149. The speaker and battery contacts are connected to the PCB by wire sets 151 and 153 respectively.

The PCB includes one or more processor chip 36, a flash memory/buffer 38, a DRAM chip 43, a transceiver chip 40, a compressed audio decoder 41 and an aerial 42. An audio digital to analogue converter 45 and an amplifier 47 are provided but not shown on the PCB.

The processor unit 81 controls and coordinates the various electronic components of the player. The processor executes software which monitors, via the sensor 16, the identity of the underlying page and the position of the player relative to the page; communicates the identity and position data to a netpage base station via the wireless transceiver 40; receives audio clip information and streaming audio data from the base station via the transceiver 40; displays clip information to the display 18; decompresses streaming audio data to the audio output via the audio decoder 45; and interprets user input captured via the user interface buttons 28. The embedded software executed by the processor is stored in the non-volatile memory 38, typically in the form of ROM and/or flash memory. Identity information unique to the player, as well as communications encryption keys, may also be stored in the non-volatile memory. During execution the processor utilizes faster volatile memory, typically in the form of a 64 Mbit (8 Mbyte) dynamic RAM (DRAM) 43.

Assuming high-quality 12:1 compression of MP3-encoded audio data, the player's memory 43 can hold 9 minutes of stereo audio. With higher compression ratios or more memory, correspondingly longer clips can be held. If streaming playback is used by the player, then only a small audio buffer is required to eliminate transmission jitter, and a significantly smaller memory may be used.

The processor unit 81 communicates with the other components via a shared bus 49. The processor, the bus, and any number of other components may be integrated into a single chip. As indicated in the block diagram, the integrated components may include the digital transceiver controller 51, the audio decoder interface 53, and the tag image sensor interface 55.

A parallel interface 57 is interposed between the bus 49 and the buttons 48, display 18, LED 31 and contact switch 39. In a more highly integrated chip, they may also include the audio decoder, the audio DAC, the tag image sensor, and the memory. The analog radio transceiver is unlikely to be integrated in the same chip, but may be integrated in the same package.

Since the player incorporates a dedicated audio decoder 41, the processor only needs to be powerful enough to control and coordinate the other components. Alternatively, the audio decoder may be omitted, and a more powerful processor can used to decode the compressed audio in software.

The transceiver 40 is typically a short-range radio transceiver. It may support any of a number of wireless transmission standards, including Bluetooth/IEEE 802.15, IEEE 802.11, HomeRF/SWAP, HIPERLAN, and OpenAir. Bluetooth/IEEE 802.15, IEEE 802.11-1997, HIPERLAN, OpenAir, and HomeRF/SWAP all support transmission rates in the range of 1 to 2 Mbit/s. IEEE 802.11b supports transmission rates of 5.5 Mbit/s and 11 Mbit/s. HIPERLAN also supports a transmission rate of 24 Mbit/s in an alternative mode. Beyond these currently-supported wireless LAN (WLAN) standards, next-generation WLAN standards promise to support transmission rates of 100 Mbit/s and beyond.

The player may alternatively be connected to the base station by cable, or may utilize a non-radio-frequency wireless transport, such as infrared. IEEE 802.11, for example, optionally utilizes an infrared transport. IrDA also utilizes an infrared transport.

The player may alternatively or additionally contain a mobile telephone transceiver for longer-range communication with a netpage server via a mobile telephone network. If the transceiver supports a third-generation ‘always-on’ packet-switched connection, then the player may download or stream audio content at will. If the transceiver only supports a circuit-switched connection, then the player may choose to connect (and potentially stream audio content) only when it encounters a hyperlink.

If the player incorporates a longer-range transceiver, then it may act as a netpage base station for wireless netpage pens and other netpage sensing devices.

Assuming 12:1 MP3 compression, the receiver must support a data rate of 118 Kbit/s. This is clearly well within the minimum capabilities of the various wireless transmission standards described above.

The PCB 14 may also be provided with a microphone 155 on its lower surface and the lower casing 13 is provided with an aperture 157 to allow sound to the microphone 155. A record switch 59 is provided to activate the microphone 155, also on the lower surface of the PCB. A record button 61 overlays the record switch 59 and is accessible via an aperture 63 in the lower casing. Preferably the button is flush with the outer surface or recessed, so as to prevent accidental activation.

The optical sensor device 16 is a netpage sensor capable of detecting invisible coded tags, as described in our co-pending patent application U.S. Ser. No. 09/721,893. The tags have preferably been printed using infrared absorptive inks. The PCB processor chips 36 includes all of the functional features of a netpage pen as discussed in our co-pending application U.S. Ser. No. 09/721,893 for decoding sensed tags. This decoded data is passed to the transceiver chip 40 for transmittal via aerial 42 to a netpage base station, such as a netpage printer or a netpage-enabled mobile telephone as disclosed in our co-pending application U.S. Ser. No. 09/721,892. Handshake and authentication between the base station and the audio player occurs before this occurs. Again reference is made to application U.S. Ser. No. 09/721,893 for a full explanation.

In the present embodiment of the invention a netpage 70 is provided. This page is tiled with invisible netpage tags 78 over some or all of the surface. For clarity only some tags are shown. The netpage 70 includes a listing 72 of audio files, available for downloading and playing. The files may be music files, speech files or other audio files, such as recordings of animal sounds or any combination of types of recordings. Each entry preferably has a summary of the entry 74 and means for the user to select the entry. This may be a separate selection button 76 or by “hyperlinking” the summary information 74 itself. Hyperlinking may be indicated by underlining of text.

A netpage consists of a printed page (or other surface region) invisibly tagged with references to an online description of the page. The tags may be printed on or into the surface of the page, may be in or on a sub-layer of the page or may be otherwise incorporated into the page. The online page description is maintained persistently by a netpage page server. The page description describes the visible layout and content of the page, including text, graphics and images. It also describes the input elements on the page, including buttons, hyperlinks, and input fields. The page descriptions of different netpages may share components, such as an image, although the netpages (and the associated page descriptions) are visibly different. The page description for each netpage may include references to these common components. A netpage allows markings made with a netpage pen on its surface to be simultaneously captured and processed by the netpage system.

Multiple netpages can share the same page description. However, to allow input through otherwise identical pages to be distinguished, each netpage is assigned a unique page identifier. This page ID has sufficient precision to distinguish between all netpages envisaged to be used in the environment of use. If the environment is small then the precision need not be as great as where the environment is large.

Each reference to the page description is encoded in a printed tag. The tag identifies the unique page on which it appears, and thereby indirectly identifies the page description. In the preferred embodiments the tag also identifies its own position on the page. Characteristics of the tags are described in more detail below.

Tags are printed in infrared-absorptive ink on any substrate which is infrared-reflective, such as ordinary paper. Near-infrared wavelengths are invisible to the human eye but are easily sensed by a solid-state image sensor with an appropriate filter. A sensor sensitive to the relative wavelength or wavelengths may be used, in which case no filters are required. Other wavelengths may be used, with appropriate substrates and sensors.

The user selects an entry by “clicking” on the hyperlink or the selection “button” and the sensor detects the tag(s) 78 in its field of view, decodes the tag(s) and transmits the decoded information to the netpage system via aerial 42. As an alternative to the collar 37, a separate selection button may be provided on the audio player to enable a user to select a link. “Clicking” the audio player against an entry or “button” involves pushing the collar 37 against the page 70 so as to cause the micro switch to close and then releasing the pressure, typically within a preset (small) time period. Whilst the micro switch is closed the image sensor device is activated and attempts to sense one or more of the tags on the page; the sensor is off when the micro switch is open to conserve power.

If the click action fails to successfully acquire and decode a tag image preferably the audio player emits an audible tone or message via the speaker 22.

When a selection has been validly made the audio player may automatically initiate audio download or streaming. Alternatively the audio player may ask for user confirmation, using the display 18 and control buttons 28. An invalid selection may also be notified to the user via the display 18 or via a dedicated LED (not shown). Communication may be via any netpage base station, such as netpage printer, or via a netpage enabled mobile telephone (see co-pending application U.S. Ser. No. 09/721,892. The netpage system determines that the decoded information equates to a request for a particular audio file or files and transmits the file(s) to the audio player 10 via the same or a different path as the request was transmitted.

In the preferred form the audio file or files are downloaded in their entirety and stored in the audio player's memory 38. The audio file may comprise one song or track or multiple songs or tracks. Alternatively a header file may be provided with an index of songs or tracks with each song or track stored in a separate file. Preferably the audio file also includes information which identifies the song or track titles, track numbers, musicians etc. and this information may be displayed on the display 18.

In use, the user may use the control buttons 28 to select any tracks stored in the memory 38. The processor 36 accesses the relevant portion of the memory, extracts the information, converts the (usually) digital format to an analogue format. Audio is routed to the speaker, or, if a plug is present in the stereo headphone socket, to the attached headphones or other external audio device. Audio may also be routed to wireless headphones via the transceiver, either directly from the base station or via the player.

Digital audio is usually sampled at 44.1 kHz, i.e. at twice the 22.05 kHz upper cutoff frequency of the 25th critical band of human hearing. Slightly higher sampling frequencies, such as 48 kHz, are sometimes used because in reality it is impractical to lowpass filter the audio with a sharp cutoff at 22.05 kHz prior to sampling. With typical quantization of 16 bits per channel, a stereo signal therefore generates 1.41 Mbit/s, and this is consequently the data rate of many common digital audio applications, including, for example, the audio compact disc (if error correction overhead is ignored).

Because the typical 1.41 Mbit/s digital audio data rate is non-trivial, there is a strong incentive to compress the digital audio signal. The most successful digital audio compression schemes have a perceptual basis, i.e. they exploit the frequency-dependence of the threshold of human hearing, and signal-dependent masking, whereby a relatively louder tone can locally raise the threshold curve and thus mask relatively softer adjacent tones. Audio compression also typically relies on traditional compression techniques such as entropy-coding. In multi-channel audio, inter-channel redundancy is also commonly exploited. A much fuller discussion of digital audio coding is given in Pohlmann, K. C., Principles of Digital Audio, 3rd Edition, McGraw-Hill, 1995, the contents of which are incorporated herein by reference.

The MPEG Audio Layer 3 (MP3) standard uses perceptual coding to achieve ‘near-CD’ and ‘CD’ quality reproduction at compression ratios of between 16:1 and 12:1, i.e. reducing the data rate from 1.41 Mbit/s to between 88 kbit/s and 118 Kbit/s.

Audio files may be compressed to reduce their size. Any compression algorithm may be used; however, the MP3 compression algorithm is, currently, an effective industry standard and so MP3 compression is used to enable maximum compatibility. A dedicated MP3 decoder 41 is provided for this purpose, the audio decoder 41 may be an STMicroelectronics STA013 decoder (STMicroelectronics, STA013 MPEG2.5 Layer III Source Decoder,). The STA013 accepts streaming data via a serial interface and is controlled via an I2C interface. Any of a number of other audio encoding standards may be supported via suitable audio decoders, including Dolby AC-3, and RealNetworks' RealAudio. The processor chip 36 may provide MP3 decoding by use of software decoding or hardware decoding. Other decoding schemes may be incorporated in the audio player together with or instead of MP3 decoding. These may be implemented in hardware or software.

The internal memory 38 is preferably 8 MB in size, enough storage for approximately 9 minutes average MP3 files. Additional storage may be provided using user replaceable memory, preferably non volatile solid state memory. Audio files may be downloaded to such user replaceable memory via the audio player 10 or via a user's personal computer. Where user replaceable memory is provided, the memory 38 provided for storage of audio files may also be implemented in user replaceable form, i.e. the audio player itself typically will have no permanent memory for storage of audio files.

In the preferred implementation the audio player downloads audio files, stores the file in memory and then plays the tracks under user control. Where the files are of significant size, downloading the entire file may take some time and so “streaming” may be implemented. In “streaming” the audio file is played as it is received, rather than once it has been fully downloaded. A file played via “streaming” may still be stored in the memory 38 for later playback.

The audio player optionally includes a microphone and a record button. It can then be used to record speech input, thus providing another kind of netpage input. Recorded speech input may, for example, be associated with a location on a netpage, in the form of an annotation, by clicking at the location with the audio player. Subsequent clicks at the same location using an audio player then cause the audio annotation to be played back. If the surfaces of physical objects are universally netpage-enabled, i.e. tagged with unique netpage tags, then audio annotations can be placed almost anywhere. Such audio annotations may be private or public. When they are private they may only be played back by their author. When they are public they may be played back by anyone.

When incorporating a microphone, the audio player can be configured to act as a wireless telephone under the control of a telephony application. Since the player lacks a user interface for dialing numbers, numbers can be selected from a netpage in the manner described in our co-pending application U.S. Ser. No. 09/721,895.

An audio clip may be associated with a netpage in the form of a hyperlink, in which case activation of the hyperlink by the audio player is ultimately handled by an application whose responsibility it becomes to provide the audio clip to the player. An audio clip may also be logically embedded as an audio clip object in a page description, in which case clip activation is ultimately handled by the page server which holds the page description. Any click in the zone of the audio clip object is interpreted by the page server as audio clip activation. In either case the actual audio clip may be stored on a separate remote server, which may become involved in the streaming playback or download of the audio clip.

The audio player can download an audio clip activated by the user into its internal memory before making it available for playback, or it can stream the audio clip on demand from the remote server in response to the user interacting with the player's playback controls.

Some of the audio files downloaded will be commercially produced songs for which the copyright owners require payment. Since the netpage system incorporates owner and device authentication, providing payment is relatively simple.

Audio files may be downloaded upon payment for a limited or infinite number of playbacks. Where the audio file is limited to a set number of playbacks the file may include a counter which is decremented after each playback. One-time “playback” may be implemented by streaming, with code to prevent recording of the file or by use of a counter with an initial value of 1. To prevent piracy, particularly where removable memory is used, the audio file stored may be modified to include the netpage ID of the audio player 10 to which it was originally downloaded. Playback may be limited to that particular audio player or to playback devices owned by the owner of the original audio player. This second option may require interaction with the netpage system for authentication.

Payment for each playback may also be implemented each time the file is played, rather than by way of a single payment. In this scenario, when the file is played, the audio player transmits information to that effect to the netpage system for debiting of the user's account. Authentication from the netpage system after debiting has occurred may be required before the audio player commences playback.

The player typically incorporates power management. After a period of inactivity the player may inactivate the status display. After a longer period of inactivity the processor may enter a power-conserving quiescent state. Power management may be coupled with the tag sensor micro-switch, allowing wake-up on page interaction. The player may also incorporate an accelerometer for this purpose.

Whilst the invention has been described with reference to the netpage system which uses invisible tags, the invention is not limited to the netpage system or the use of invisible tags. If desired, the invention may utilize tags or codes which are visible to the average unaided human eye, such as bar codes. The tags need not merely encode an identity which is then used to look up the relevant files. The tags may encode instructions at a higher level. For example a tag may encode an instruction of “play the track entitled X by the artist Y”. If invisible tags are used they need not be limited to the tags disclosed in relation to the netpage system. Other tagging systems are available and any suitable tagging system may be used. The invention is not limited to the use of inks which absorb certain wavelengths or fluoresce certain wavelengths. Magnetic inks, surface modification, including apertures, modification of the structure of the substrate itself all fall within the scope of the invention. The systems and methods to link the audio player of the present invention and the source of the audio files are not limited to netpage systems. An audio player may be linked by a cable to a single computer, rather than a network of computers.

The present invention has been described with reference to a preferred embodiment and number of specific alternative embodiments. However, it will be appreciated by those skilled in the relevant fields that a number of other embodiments, differing from those specifically described, will also fall within the spirit and scope of the present invention. Accordingly, it will be understood that the invention is not intended to be limited to the specific embodiments described in the present specification, including documents incorporated by cross-reference as appropriate. The scope of the invention is only limited by the attached claims. 

1. A method of playing audio data by a portable device, said method comprising the steps of: sensing, by an optical sensor of the portable device, at least one tag on a surface, each tag encoding an identity of the surface and a location of that tag on the surface; recording audio data by an audio system of the portable device; determining, by a processor of the portable device, the identity of the surface and the location of the tag sensed by the optical sensing device on the surface; communicating by the portable device the audio data, the identity of the surface and the location of the tag to a computer system; associating, by the computer system, the audio data with the identity of the surface and the location of the tag; wherein, upon subsequent sensing of the tag by the optical sensor, the method comprises the further steps of: communicating by the portable device the identity of the surface and the location of the tag to the computer system; retrieving, by the computer system, the audio data associated with the identity of the surface and the location of the tag; communicating the audio data from the computer system to the portable device; and playing back the audio data retrieved by the portable device.
 2. The method of claim 1, wherein the computer system is remote from the sensing device.
 3. The method of claim 1, wherein communication between the portable device and the computer system is wireless.
 4. The method of claim 1, wherein the recording step is initiated by actuation of a button on the portable device.
 5. The method of claim 1, wherein the computer system stores in a memory the association between the identity of the surface, the location of the tag and the audio data. 